Excel Serial Date Converter
Excel stores dates as serial numbers — days counted from December 30, 1899. Paste a serial number to see the date, or pick a date to get its serial, with instant results in either direction.
Enter your numbers
Your results
| Serial number | — |
|---|---|
| Date | — |
| Day of week | — |
How to use this calculator
Choose a direction: Serial → Date or Date → Serial. Enter a serial number (for example 44927) or pick a date, and the conversion appears instantly.
How it works
Date = December 30, 1899 + serial days (the 1900 date system). So serial 44927 lands on January 1, 2023. Note: Excel wrongly treats 1900 as a leap year (a bug inherited from Lotus 1-2-3), so serials below 61 are off by one day from the real calendar — the converter flags those.
Frequently asked questions
What is an Excel serial date?
Excel stores dates as days since December 30, 1899 — so 44927 means January 1, 2023.
Why is 1900-02-29 a problem?
Excel wrongly treats 1900 as a leap year (a Lotus 1-2-3 bug); serials below 61 are off by one day.
What about the 1904 date system?
Mac-era workbooks may use 1904-01-01 as day zero — this converter uses the standard 1900 system.
How do I convert in Excel itself?
Format the cell as a date, or use TEXT(serial,"yyyy-mm-dd").